The invention is based on a grinding body for an electric grinding tool, having the generic characteristics of the preamble to claim 1; a grinding medium for an electric grinding tool, having the generic characteristics of the preamble to claim 6; and an electric grinding tool, having the generic characteristics of the preamble to claim 8.
For machining surfaces by grinding, delta, eccentric or oscillation grinders are for instance known. For machining the surface, they have a motor-driven grinding plate of polyurethane foam, on which a grinding body is mounted. The grinding body is sandpaper or grinding cloth to which granular abrasives are applied. The sandpaper or grinding cloth has a piece of velour on its side facing away from the granular abrasives, with which it is connected to the grinding plate via a barbed strip mounted there. However, only short service lives can be attained with the known grinding body, since when grinding hard surfaces, the granular abrasives wear down rapidly, and they quickly become clogged with paint when grinding painted surfaces. Such grinding bodies then have to be replaced. Moreover, the material-removal capacity is low, even when the grinding body is fresh, and so the same place has to be machined for a very long time until the desired grinding result is achieved.
A grinding body of the invention having the characteristics of claim 1, a grinding medium of the invention having the characteristics of claim 6, and an electric grinding tool of the invention having the characteristics of claim 8 have the advantage over the prior art of a long service life and high material-removing capacity.
In a grinding body of the invention, instead of sandpaper or grinding cloth, a steel band is used as the carrier plate, on which a granular abrasive comprising hard-metal granular abrasive is applied. Because a steel band is used as the carrier plate, the carrier plate does not become compressed and hence deformed like an accordion. Moreover, using a steel band makes it possible to use a hard-metal granular abrasive. This hard-metal granular abrasive is applied to the steel band using a special soldering process. However, since this soldering process is not definitive for the invention, it will not be explained in further detail in the present patent application. Using a hard-metal granular abrasive as the granular abrasive means that an extremely long service life is attained, since wear is hardly noticeable. Even when surfaces clogged with paint are ground, the grinding body does not have to be thrown away when it becomes clogged with paint; instead, the paint can simply be brushed out or knocked off. After that, the grinding body is again ready for use and is in practically the same state it was originally. Moreover, using hard-metal granular abrasive also makes for more-aggressive grinding, so that a high material-removal capacity is achieved.
Preventing compression of the steel band is preferably attained by providing that it has a tensile strength of more than 1100 N/m2, in particular more than 1300 N/m2, and preferably 2000 N/m2. It is especially preferred if the steel band has a chromium content of between 14% and 20%, in particular 16.7%, and a nickel content of between 4% and 9%, in particular 6.64%.
The attempt is preferably made to embody the steel band as thinly as possible. The thinner it is, the lower its weight also is. An excessive thickness, at high rotary speeds, creates mechanical problems, such as imbalances. It is therefore advantageous if its thickness is less than 1 mm, in particular less than 0.3 mm, and preferably even only 0.2 mm. At a thickness of 0.3 mm, the grinding body has approximately the same weight as the conventional grinding bodies used until now, that were made of sandpaper with granular abrasives and a velour layer. The thinner the steel band is, the greater its tensile strength must be to prevent compression. At a tensile strength of 2000 N/m2, it is accordingly also possible to use the especially preferred, quite thin steel band of only 0.2 mm in thickness. Conversely, that cannot be done if the tensile strength is only 1100 N/m2.
Suction extraction of the grinding dust produced in grinding is possible by means of first suction-extraction holes embodied in the steel band. Hence the user of the electric grinding tool is not burdened by grinding dust, which is usually quite fine and by becoming deposited in the respiratory system is harmful to health.
In a grinding medium of the invention, a grinding body of the invention is glued, screwed, interlocked or directly sprayed onto the base plate directly in the form of foam. Gluing the steel band to the polyurethane base plate makes very simple and very inexpensive fastening of the two parts possible. Screwing the two parts together makes it possible, in the event of possible wear of the grinding body, which can never be precluded entirely, to replace only the grinding body without having to change the base plate as well. This reduces the costs to the user.
It is advantageous if the base plate has second suction-extraction holes, which are disposed under the first suction-extraction holes of the steel band. This assures optimal suction extraction of the grinding dust produced during operation. The result is the least possible burden on the user.
Further advantageous features of the invention are the subject of the dependent claims.